DESCRIPTION: (Applicant's Abstract) Cannabinoid receptors, which mediate the effects of the principal psychoactive ingredient of marijuana and hashish, have been found in large numbers throughout the brain. There is now substantial evidence, including immunohistochemical studies I have performed in our laboratory, that they are also present in the retina. The question is where exactly are they, and what are they doing there. The intent of this project is to use immunohistochemical and electrophysiological techniques to determine where in the retina the cannabinoid receptor is expressed and to characterize the function of the putative ligands anandamide and 2-AG via the investigation of several known and likely mechanisms found in other parts of the brain as well as any others suggested by the immunohistochemical studies.